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123 lines
4.5 KiB
Python
123 lines
4.5 KiB
Python
from typing import List, Tuple
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from ...pipeline import Lemmatizer
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from ...tokens import Token
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class DutchLemmatizer(Lemmatizer):
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@classmethod
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def get_lookups_config(cls, mode: str) -> Tuple[List[str], List[str]]:
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if mode == "rule":
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required = ["lemma_lookup", "lemma_rules", "lemma_exc", "lemma_index"]
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return (required, [])
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else:
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return super().get_lookups_config(mode)
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def lookup_lemmatize(self, token: Token) -> List[str]:
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"""Overrides parent method so that a lowercased version of the string
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is used to search the lookup table. This is necessary because our
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lookup table consists entirely of lowercase keys."""
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lookup_table = self.lookups.get_table("lemma_lookup", {})
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string = token.text.lower()
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return [lookup_table.get(string, string)]
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# Note: CGN does not distinguish AUX verbs, so we treat AUX as VERB.
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def rule_lemmatize(self, token: Token) -> List[str]:
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# Difference 1: self.rules is assumed to be non-None, so no
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# 'is None' check required.
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# String lowercased from the get-go. All lemmatization results in
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# lowercased strings. For most applications, this shouldn't pose
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# any problems, and it keeps the exceptions indexes small. If this
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# creates problems for proper nouns, we can introduce a check for
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# univ_pos == "PROPN".
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cache_key = (token.lower, token.pos)
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if cache_key in self.cache:
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return self.cache[cache_key]
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string = token.text
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univ_pos = token.pos_.lower()
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if univ_pos in ("", "eol", "space"):
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forms = [string.lower()]
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self.cache[cache_key] = forms
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return forms
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index_table = self.lookups.get_table("lemma_index", {})
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exc_table = self.lookups.get_table("lemma_exc", {})
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rules_table = self.lookups.get_table("lemma_rules", {})
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index = index_table.get(univ_pos, {})
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exceptions = exc_table.get(univ_pos, {})
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rules = rules_table.get(univ_pos, {})
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string = string.lower()
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if univ_pos not in (
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"noun",
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"verb",
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"aux",
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"adj",
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"adv",
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"pron",
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"det",
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"adp",
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"num",
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):
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forms = [string]
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self.cache[cache_key] = forms
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return forms
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lemma_index = index_table.get(univ_pos, {})
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# string is already lemma
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if string in lemma_index:
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forms = [string]
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self.cache[cache_key] = forms
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return forms
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exc_table = self.lookups.get_table("lemma_exc", {})
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exceptions = exc_table.get(univ_pos, {})
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# string is irregular token contained in exceptions index.
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try:
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forms = [exceptions[string][0]]
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self.cache[cache_key] = forms
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return forms
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except KeyError:
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pass
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# string corresponds to key in lookup table
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lookup_table = self.lookups.get_table("lemma_lookup", {})
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looked_up_lemma = lookup_table.get(string)
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if looked_up_lemma and looked_up_lemma in lemma_index:
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forms = [looked_up_lemma]
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self.cache[cache_key] = forms
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return forms
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rules_table = self.lookups.get_table("lemma_rules", {})
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oov_forms = []
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for old, new in rules:
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if string.endswith(old):
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form = string[: len(string) - len(old)] + new
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if not form:
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pass
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elif form in index:
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forms = [form]
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self.cache[cache_key] = forms
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return forms
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else:
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oov_forms.append(form)
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forms = list(set(oov_forms))
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# Back-off through remaining return value candidates.
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if forms:
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for form in forms:
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if form in exceptions:
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forms = [form]
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self.cache[cache_key] = forms
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return forms
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if looked_up_lemma:
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forms = [looked_up_lemma]
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self.cache[cache_key] = forms
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return forms
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else:
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self.cache[cache_key] = forms
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return forms
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elif looked_up_lemma:
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forms = [looked_up_lemma]
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self.cache[cache_key] = forms
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return forms
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else:
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forms = [string]
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self.cache[cache_key] = forms
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return forms
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